Radical polymers are formed by radical polymerization of one (homopolymer) or several radically polymerizable monomers (copolymer). Depending on the functionality of the polymerized monomers, either linear (monofunctional monomers) or crosslinked (di- or multifunctional monomers) polymers are obtained.
As is generally known, radical polymerizations can be carried out in matter (bulk polymerization), solution, suspension or emulsion. Radical-forming initiators which form radicals by thermolysis, photolysis or redox-reaction are added to initiate the polymerization. The radical polymerization proceeds according to a chain-growth mechanism in which the polymerization-initiating radicals, the so-called primary radicals, add onto the double bond of the monomers. The thus-formed initiator radicals add many further monomer molecules in a rapid growth reaction until the growth of the polymer radicals is terminated by combination or disproportionation and the finished macromolecules form.
In the case of radical polymerization chain transfers often occur. Here the polymer radical transfers an electron to a second molecule by substitution with another atom, e.g. to a monomer, solvent or polymer molecule. The newly-formed radical can again initiate a polymerization. The number average molar mass of the polymer can be regulated in a targeted manner by the addition of chain transfer agents, so-called chain regulators, (cf. H. G. Elias, Makromoleküle, Vol. 1, 6th Edition, Wiley-VCH, Weinheim etc. 199, 299-352). The known chain transfer agents include, for example, the mercaptans, which, through the transfer of an H atom, form thiyl radicals, which then initiate a new polymerization sequence.
Reagents containing double bonds which react according to a radical addition-fragmentation chain transfer mechanism (AFCT) have proved particularly worthwhile as chain transfer agents. Sulphur compounds, such as allyl sulphides, allyl sulphones, dithioesters, dithiocarbamates, xanthates and trithiocarbonates are particularly effective as AFCT reagents and are well studied (cf. G. Moad, E. Rizzardo, S. H. Thang, Polymer 49 (2008) 1079-1131). Moreover, reversible AFCT reagents (RAFT reagents), such as e.g. dithioesters, dithiocarbamates, trithiocarbonates or xanthates are known from controlled radical polymerization (cf. e.g. Moad et al., loc. cit.).
U.S. Pat. No. 2,694,699 describes the homo- and copolymerization of α-sulphonyloxyacrylates. Alkyl mercaptans can be added as chain regulators.
U.S. Pat. No. 5,932,675 discloses a process for the preparation of polymers with low molecular weight by radical polymerization, wherein the molecular weight is controlled by the addition e.g. of α-(t-butanethiomethyl)styrene as chain transfer reagent.
The use of the known transfer-active compounds makes it possible to control the molecular weight of the polymers but has the disadvantage that it leads to a significant reduction in the polymerization rate. The use of α-sulphonyloxyacrylates, alkyl or aryl sulphonic acid vinyl-esters as chain transfer reagents is not known.